With the rapid increase of Internet traffic, the wavelength division multiplexing (WDM) transport network has gradually been widely used. Typically, the following technologies are used in the optical network: 1) optical add-drop multiplexing (OADM), in which a given wavelength can be inserted into or removed from an optical fiber; 2) wavelength routing, in which the wavelength of an input optical fiber can be routed to an output optical fiber; 3) wavelength conversion, in which a wavelength can be converted to another wavelength, and the existence or non-existence of wavelength conversion capability will affect the solution to routing and wavelength assignment (RWA); 4) optical switching, in which wavelength switching from one optical fiber to another can be implemented. The aforementioned technologies enable the transport network to provide more flexible functionalities.
Currently, functions of a switching matrix are limited and an optical transponder does not support full conversion of all optical wavelengths, thus when an optical link is assigned and an optical path is established, wavelength continuity limitations which cause potential congestion problems are still required to be considered. The RWA can be divided into centralized RWA and distributed RWA, important difference between which is that in the centralized RWA, each node in a network is aware of wavelength resource information of all nodes in the whole network, and the wavelength assignment algorithm is only performed in a source node. The RWA can be divided into two processes: Routing (R) and wavelength assignment (WA). In the R process, route calculation with constraint conditions, including uplink and downlink constraint conditions of a first node and a last node, optical fiber connectivity within a node, node wavelength resources, etc., are performed. The WA process is responsible for assigning wavelength resources to the calculated routes to establish an optical path (service tunnel). In the centralized RWA process, for a topology network shown in FIG. 3, in order to find a working route between node 1 and node 4, K=4 routes, 1-2-4, 1-2-5-4, 1-3-2-4 and 1-3-2-5-4, are firstly calculated in the R process, there being a number of nodes on each route; and secondly, wavelength assignment (WA) is performed, including determining availability or unavailability of the routes, and connectivity within the nodes. For example, there are 80 waves in each entrance and exit interface on the route 1-2-4: 1->2 (80 waves), 2->1 (80 waved), 2->4 (80 waves) and 4->2 (80 waves), and a wave that is not occupied by all nodes on the route is selected from these waves. This process specifically comprises the following steps. In step 101, an optical network is established, connections between fibers within the optical network are configured, and connections between fibers at first and last nodes (transmission interfaces) are configured. In step 102, a service tunnel from node 1 to node 4 is attempted to be established. In step 103, the K-shortest routing algorithm is performed to return K routes containing wavelength resource information, wherein a recursive algorithm is used to calculate the routes, and K is set to be 2. If two returned routes are 1->2->4 and 1->2->5->4 respectively, the process proceeds to step 104; and if it can be determined that the routes have not been found and there are no remaining routes, the process directly proceeds to step 106. In step 104, it is determined whether wavelength assignment is performed for each route, if the route is determined to be unavailable, the process returns to step 103, otherwise, the process proceeds to step 105. In step 105, the wavelength assignment is performed for all the found routes as working routes. In step 106, the process ends, and a prompt of query failure or a corresponding found working route is provided.